High operating frequencies are desirable for power conditioning equipment (such as power supplies, power amplifiers, and lamp ballasts) in order to reduce the size of the magnetic components used therein. Unfortunately, however, it has been heretofore impossible to substantially reduce the size of magnetic components because the operating flux density would have to be reduced too much for proper operation and still have acceptable losses at high frequencies. In particular, while at low frequencies the operating flux density can exceed 10,000 Gauss using bulk ferromagnetic material, the operating flux density to achieve acceptable losses in the megahertz range is from about 20 to 400 Gauss, which is too low for proper operation.
Another problem with magnetic components is high profile. In the present state of the art, devices having a height on the order of 0.1 inch can be constructed with machined ferrites and high density interconnect (HDI) windings using multipole designs, such as described in U.S. patent application No. 08/043,166 of W. A. Roshen, C. S. Korman and W. Daum, filed Apr. 1, 1993, assigned to the instant assignee and incorporated by reference herein. A further reduction in the height of power magnetic devices is difficult because machined ferrites are fragile.
Yet another problem with the use of ferrites is their relatively low Curie temperature which makes them unsuitable for high temperature applications. Powdered iron is also unsuitable for high temperature use due to the properties of available binders.
Accordingly, it is desirable to provide high power magnetic circuit components having a reduced height and weight which are capable of operating at high flux density levels at high frequencies (e.g., 1-10 MHz) and at high temperatures. Furthermore, such magnetic circuit components should be compatible with high density packaging techniques, such as HDI techniques.